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cloudsweeper

Bulging Craters, Anyone??

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Posted (edited)

Splendid views of Clavius in the heavily-cratered southern highlands near the terminator yesterday - the arc of craterlets of decreasing sizes within, plus lots of very small ones. 

Anyway.  I have occasionally seen lunar photos and thought the craters appeared to be convex/bulging, and put it down to the lighting conditions, never thinking it was in fact my perception, until that perception changed.  The pic attached is one such - the effect may or may not work with this image.

And last night, while enjoying Clavius and environs, I saw the effect with the Moon itself!  Clavius and all the craters around it all got reversed and bulged out, changing the landscape completely.  A very strange effect, and one I have not experienced before.  Very odd and very interesting - at one point I was able to flip the view more or less at will!

There must be lots of veteran Moon-viewers out there who have seen this (please let me know!), although I don't recall any references to it.  It certainly came as surprise!

Doug.

(Bresser Dob, x212.)

P1070037.JPG

Edited by cloudsweeper
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32 minutes ago, cloudsweeper said:

Splendid views of Clavius in the heavily-cratered southern highlands near the terminator yesterday - the arc of craterlets of decreasing sizes within, plus lots of very small ones. 

Anyway.  I have occasionally seen lunar photos and thought the craters appeared to be convex/bulging, and put it down to the lighting conditions, never thinking it was in fact my perception, until that perception changed.  The pic attached is one such - the effect may or may not work with this image.

And last night, while enjoying Clavius and environs, I saw the effect with the Moon itself!  Clavius and all the craters around it all got reversed and bulged out, changing the landscape completely.  A very strange effect, and one I have not experienced before.  Very odd and very interesting - at one point I was able to flip the view more or less at will!

There must be lots of veteran Moon-viewers out there who have seen this (please let me know!), although I don't recall any references to it.  It certainly came as surprise!

Doug.

(Bresser Dob, x212.)

P1070037.JPG

It happens fairly often to me and I just have to look away from the eyepiece for a few seconds..:smiley:

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I didn't experience the effect last night but I had the problem, if you can call it that, last month. Like you, it happened looking at the heavily cratered area around Clavius. It was so bad at one stage during that particular night that I had problems seeing the craters as concave. They just kept jumping back to convex at almost every viewing after looking away. A curious and confusing at first optical illusion. The mind plays tricks eh.

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Works on both these examples for me, especially impressed with the lizard...

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My problem is that, if it happens, I can't get them to pop back in!

There are satellite images of valleys and river estuaries on earth that pop out for me too:

1338721791_space1-colorado-river1.png.1ad6e009c0dcb665df82e33102f19f5f.png

Mars too!

Perspective_view_of_Osuga_Valles.thumb.jpg.eee22c19fbd167224f504543781069e8.jpg

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On 14/05/2019 at 08:23, Saganite said:

It happens fairly often to me and I just have to look away from the eyepiece for a few seconds..:smiley:

That is so weird. When I first saw the OP image the craters looked like they were indeed bulging. When I saw your image, and looked again at OP image, I saw no bulging.

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I've been seeing this effect since I was young, starting with a photo used to illustrate an article on making plaster-of-paris lunar craters. No matter how I looked at it, the craters always looked like mounds unless I rotated the image.

I think it's all down to lighting angles and expected perceptions. We generally expect things to be lit from above, so for a crater the higher wall would be in shadow and the lower would be lit. When presented with an image that's lit from below the confusion starts because the shadow is now on the lower edge

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I see this effect sometimes and it takes quite a lot of concentration to reverse the image until the craters look like craters.  I think it is similar when you look at a 3D image and can;t see the object within to start with, then after some concentration the picture appears.  I almost have to cross my eyes in order to achieve this or to undo the convex craters into concave craters. 

Carole 

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Yes, I too am familiar with that phenomenon... it's the side effect of looking at the featured with one eye and seeing it in 2D.. depending on which hemipshere of your brain processes the view will depend whether you can see it as a bulge or indentation.

If you train your brain with practice, you will be able to switch that all will.... exactly the same reason for the attached ballerina spinning left or right.... again, with concentration and practice you can change the spin direction at will.

http://www.mindmagician.org/dancer.aspx

 

 

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I can at times see the bulging, but if I look at it long enough, or look away, I can see the craters and canyons, and then it will switch again.  The phenomenon has been discussed on CN and Wikipedia.  

Interestingly, when you see the "lizard" the sun appears to come from the right of the frame, lighting the lizard's right side, but when you see the canyon, the sun comes from the left, lighting the right canyon wall in the frame, and shadowing the left canyon wall.

Amazing how our brains work. When search this phenomenon as it relates to other images, I came across this really cool video from youtube:  

Clear skies!

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